Interestingly, there are ingredients in the Zelda recipe that Skyrim could do with. They are: 1) a consistent level of engaging fun, 2) a stark contrast between level design themes, 3) quests and plot components that feature interactive puzzles. Now before you bite my head off hear me out.
1. A consistent level of engaging fun.
Now when we play Zelda we generally enjoy the game all the way through, there are new elements to interact with many of which we haven't seen before. With Oblivion there was much to explore but you get to the stage where when you've seen one thing, you've seen them all. Indoor items like crockery eventually looks repetitive, NPC faces and clothes are often copies of the same base set, enemies all behave in a similar manner, etc. So, what Bethesda could learn from Zelda is to be more engaging - that's not to say that this wasn't achieved (just think of the Whodunit? quest). But that said, its about a consistent level of fun, not a sporadic sprinkling (as in Oblivion) where you're as likely to be bored with something as utterly amazed.
2. A stark contrast between level design themes.
One thing Oblivion suffered poorly with was a lack of diversity in its level design. Once you visited one cave you noticed a copy and paste theme. Although Skyrim level designers are a larger team now and are hand rendering the design for that human element there is still the problem of what you use the same base sets of walls, floors, furniture, etc - it gets repetitive. Whether there is a stark contrast between different cities we will not know until we play the game. But in Zelda each area was significantly different from the last and that made it exceptionally interesting. Of course we had areas we didn't like but that's normal. But going from desert palace, lush forest, regal castle, to open plains, etc - made the experience rather epic in its own way. I am hoping we will not have mountains, dungeons, cities, tundra - alone. But a more diverse landscape that invokes a sense of discovery to keep our eyes bulging. And yes the Zelda world was boxed in but if those elements could be encouraged in a more cinematic game like Skyrim the game would be become more than breathtaking - here's hoping.
3. Quests and plot components that feature interactive puzzles.
Oblivion touched on this but it failed to continue the tradition further in the game. We had the puzzle of tracking down a cult, a magic sensitive Ayleid ruin barrier, a murder mystery (Whodunit?), figuring out how to shut down an Oblivion gate (well the first gate), etc. But that's where the game seemed to end with its interactive puzzles. What Zelda has in this regard is a constant barrage of puzzles that require you to think them through and consider your options. I'm not saying that we should be in puzzle dungeons like in Zelda, but that element of having to puzzle out how to tackle a problem in order to progress is a very engaging element that I think we could all benefit from.
To sum up, I'm not saying Skyrim will be bad - but what I am saying is that if it can learn from what other game developers are doing right and use those inspirations to further develop the Elder Scrolls Series (not change it completely) then we could possibly have a game that will outlive Morrowind.